Add optional anyhow dependency (under the same feature flag) to implement IntoLua for anyhow::Error

Author: khvzak

Cargo.toml

@@ -41,6 +41,7 @@ async = ["dep:futures-util"]
 send = ["parking_lot/send_guard"]
 serialize = ["dep:serde", "dep:erased-serde", "dep:serde-value"]
 macros = ["mlua_derive/macros"]
+anyhow = ["dep:anyhow"]
 
 [dependencies]
 mlua_derive = { version = "=0.10.0-beta.1", optional = true, path = "mlua_derive" }
@@ -52,6 +53,7 @@ serde = { version = "1.0", optional = true }
 erased-serde = { version = "0.4", optional = true }
 serde-value = { version = "0.7", optional = true }
 parking_lot = { version = "0.12", features = ["arc_lock"] }
+anyhow = { version = "1.0", optional = true }
 
 ffi = { package = "mlua-sys", version = "0.6.3", path = "mlua-sys" }
 

src/conversion.rs

@@ -254,6 +254,14 @@ impl FromLua for Error {
     }
 }
 
+#[cfg(feature = "anyhow")]
+impl IntoLua for anyhow::Error {
+    #[inline]
+    fn into_lua(self, _: &Lua) -> Result<Value> {
+        Ok(Value::Error(Box::new(Error::from(self))))
+    }
+}
+
 impl IntoLua for RegistryKey {
     #[inline]
     fn into_lua(self, lua: &Lua) -> Result<Value> {

src/error.rs

@@ -454,7 +454,7 @@ impl ErrorContext for Error {
     }
 }
 
-impl<T> ErrorContext for StdResult<T, Error> {
+impl<T> ErrorContext for Result<T> {
     fn context<C: fmt::Display>(self, context: C) -> Self {
         self.map_err(|err| err.context(context))
     }
@@ -496,6 +496,16 @@ impl serde::de::Error for Error {
     }
 }
 
+#[cfg(feature = "anyhow")]
+impl From<anyhow::Error> for Error {
+    fn from(err: anyhow::Error) -> Self {
+        match err.downcast::<Self>() {
+            Ok(err) => err,
+            Err(err) => Error::external(err),
+        }
+    }
+}
+
 struct Chain<'a> {
     root: &'a Error,
     current: Option<&'a (dyn StdError + 'static)>,

tests/error.rs

@@ -72,3 +72,26 @@ fn test_error_chain() -> Result<()> {
 
     Ok(())
 }
+
+#[cfg(feature = "anyhow")]
+#[test]
+fn test_error_anyhow() -> Result<()> {
+    use mlua::IntoLua;
+
+    let lua = Lua::new();
+
+    let err = anyhow::Error::msg("anyhow error");
+    let val = err.into_lua(&lua)?;
+    assert!(val.is_error());
+    assert_eq!(val.as_error().unwrap().to_string(), "anyhow error");
+
+    // Try Error -> anyhow::Error -> Error roundtrip
+    let err = Error::runtime("runtime error");
+    let err = anyhow::Error::new(err);
+    let err = err.into_lua(&lua)?;
+    assert!(err.is_error());
+    let err = err.as_error().unwrap();
+    assert!(matches!(err, Error::RuntimeError(msg) if msg == "runtime error"));
+
+    Ok(())
+}